GB2088325A - Elevating working platforms - Google Patents

Abstract

In lifting apparatus comprising a base (1), a platform (5), and a pantographic lifting mechanism (4) disposed between the base and the platform, the lifting mechanism, which comprises superimposed X-link units, is operated by lever arms (18, 19) rotatably mounted intermediate the central and end pivot points of a link arm 7, and rotated by means (29) provided on the link arm. The free end of each lever arm (18, 19) slides along an adjacent link arm, whereby the rotation of the lever arm expands the lifting mechanism. <IMAGE>

Description

SPECIFICATION Lifting apparatus The present invention relates to lifting apparatus for elevating a working platform for use at elevated positions.

For working, repairing, painting and other purposes at high places, lifting apparatus having a work platform for carrying workers and materials thereon is used. Many of the conventionally used lifting apparatus have employed pantographic lifting mechanism, each X-link unit of which is expansible by hydraulic cylinders to open the link levers directly.

In this type of conventional lifting mechanism, the hydraulic cylinder is fixed only to the base, and the piston rod of the cylinder is connected with a lowermost link lever of the lifting mechanism.

Because of such mechanism, the upper link levers start to expand later than the lower link levers, as a result, the whole pantograph cannot be smoothly actuated.

In order to overcome the above described drawbacks, the present invention provides a lifting apparatus in which the pantographic lifting mechanism expands vertically by actuating lever arms supportedly provided between two pantograph units.

Thus, lifting apparatus according to the invention comprises a base; a platform; a lifting mechanism of pantographic type disposed between the base and the platform and constructed with a plurality of superimposed Xlink units, each of said X-link units comprising a pair of link levers rotatably connected to each other at a central portion to form an X-link; and an actuating mechanism comprising a lever arm rotatably mounted on one of the X-link units between said central portion and an end of one of said link levers, and driving means on said one of the link levers for rotating said lever arm, one end of said lever arm being engaged with the other link lever connected with the end of said link lever carrying said driving means, whereby the rotation of the lever arm expands the pantographic lifting mechanism.

The invention will be more fully understood by way of example from the following description of elevating platforms in accordance therewith, reference being made to the accompanying drawings, in which Figure 1 is a side view showing a first form of lifting apparatus, the lifting mechanism being shown in full line in its retracted position and in chain line in its elevated position; Figure 2 is a perspective view showing the lifting apparatus of Figure 1 with the X-link units fully expanded; Figure 3 is an enlarged perspective view showing the link lever portion; Figure 4 is a schematic illustration of another form of lifting mechanism; and Figure 5 is a side view showing fully expanded the X-link units of Figure 4.

Referring to Figures 1 and 2, numeral 1 designates a vehicle body, 2 are wheels supported at four corners of the body, 3 are extensible jacks also secured to the four corners of the body 1 (in this embodiment, the vehicle 1 is shown as a trailer). A lifting mechanism 4 is attached to the vehicle body 1 by hinge pins and a platform 5 is connected by hinge pins on the upper end of the lifting mechanism. Handrails 6 are provided circumferentially on the platform.

The pantographic lifting mechanism 4 comprises a plurality of connected X-link units.

Each X-link unit comprises two pairs of link levers 7 which are pivotally connected to each other to form an X-shape; as each pair is identical to the other, only one will be described. A plurality of sets of X-link units are superimposed and adjacent units are rotatably connected together by hinge pins 8. One end of the lowermost X-unit is connected by pins 9 to the body 1, and the other end is supported by a roller 10 on the body 1, while one end of the uppermost X-unit is connected to the work platform 5 by pins 12, and the other end is connected to a slider 1 3 by pins 14. The roller 10 is engaged with a guide rail 11 fixedly provided on the body 1, while each slider 14 is engaged with a groove 1 5 fixedly provided on the underside of the platform 5.

Between the centre and ends of the two middle link levers 7, driving shafts 16, 17 are rotatably supported, and have secured to them pairs of lever arms 1 8, 1 9 respectively. Each lever arm 1 8, 1 9 carries at its end a roller 20, 21, the end of which is engaged with respective fixed rails 22, 23 provided on the lever 7 of the next adjacent X-unit.

Each driving shaft 1 6, 1 7 has respective sprocket wheels 24, 25 which engage chains 26, causing the two shafts 1 6, 1 7 to turn together. Auxiliary cross-struts 27 and 28 are provided at both ends of the pair of parallel levers 7 carrying the shafts 1 6 and 1 7. Connected at the centre of these connecting rods 27, 28 are hydraulic cylinders 29, 30 which function as driving device for the link units. Actuating rods 31 and 32 are fixedly bridged between the pair of chains 26. The actuating rods 31 and 32 have respective rod 33, 34 of cylinders 29, 30 connected to the centre thereof.

The following is the description of the operation of the lifting apparatus of Figures 1 to 3: The work platform 5 is shown in its lowermost position in full lines in Figure 1; lever arms 1 8, 19 are then positioned parallel to the X-link units which are superimposed and folded flat under the work platform 5. In order to elevate the work platform 5, hydraulic cylinders 29, 30 are actuated to extend rods 33, 34 from the cylinders 29, 30.

With the extension of rods 33, 34, actuating rods 31,32 move to drive the chain 26, which go around sprocket wheels 24, 25, so that the sprocket wheels are rotated in the direction of the arrows shown in Figure 1. The rotation of the sprocket wheels 24, 25 rotate driving shafts 1 6, 1 7 and lever arms 1 8, 1 9, so that the rollers 20, 21 carried at the ends of lever arms 1 8, 1 9 urge the rail 22, 23 to expand the pantograph. The rotations of the lever arms 1 8, 19 cause the opening angle between the X-links to expand gradually, resulting in the upward stretch of the pantographic lifting mechanism 4. Accordingly, the working platform 5 on the lifting mechanism 4 is elevated.The broken lines of Figure 1 show the fully elevated condition of the platform 5, which is also shown in Figure 2.

In order to lower the platform 5, the pressure in the hydraulic cylinder is reduced to retract the rods 33, 34 back into the cylinder 29, 30 and to rotate the chain 26 in the opposite direction to that of the arrow in Figure 1.

Owing to the reverse rotation of the lever arms 18, 19 and also owing to the descent of the platform 5 under its own weight, the opening angle made by adjacent two link levers 7 of each unit becomes smaller.

Figures 4 and 5 show a modification of the lifting apparatus, in which each of driving shafts 16, 17 is connected to the centre of respective lever arms 35, 36. Each end of the lever arms 35, 36 has a V-shaped actuating member 37, 38 in the form of a bell crank lever connected rotatably at the corner of the member. An auxiliary rod 39 connects the sprocket wheel 24 or 25 and an end of actuating member 37. That is, a parallelogram is made by sprocket wheel 24 or 25, lever arm 35 (36), actuating member 37 (38) and auxiliary rod 39 (40).

Carried at the other end of each actuating member 37 (38) is a roller 41 (42) which engages with rail 43 (44, 45, 46) provided on the lever 7.

In this embodiment, rotation of sprocket wheels 24,25 cause driving shafts 16, 17 to rotate lever arms 35, 36 so that rollers 41,42 carried on actuating members 37, 38 push the link levers 7 of adjacent X-units away from the central X-unit to elevate the platform 5. When the lever arm 35 (36) is rotated, the actuating member 37 (38) is rotated by auxiliary rod 39 (40) until the roller 41 (42) becomes aligned with lever arm 35 (36).

Figure 5 shows the relation of the lever arms 35, 36 and the actuating members 37, 38 when the platform is fully elevated to a higher position.

Thus, because rollers 41,42 in this embodiment move along rails 43-46 for a longer distance than rollers 20,21 of the previous embodiment shown in Figure 1, for the same rotary angle of lever arms 18, 19 and lever arms 35, 36, X-link units 7 of the mechanism shown in Figure 4 stretch wider than the link units of the embodiment shown in Figure 1, resulting in higher elevation of the platform 5.

According to the above-described construction of the present invention, which uses lever arms to actuate the pantographic lifting mechanism and to expand each of the X-link units, the operation becomes smoother and the expansion of each X-link unit becomes uniform and steady.

Claims (4)

1. Lifting apparatus comprising a base: a platform; a lifting mechanism of pantographic type disposed between the base and the platform and constructed with a plurality of superimposed X-link units, each of said X-link units comprising a pair of link levers rotatably connected to each other at a central portion to form an X-link; and an actuating mechanism comprising a lever arm rotatably mounted on one of the X-link units between said central portion and an end of one of said link levers, and driving means on said one of the link levers for rotating said lever arm, one end of said lever arm being engaged with the other link lever connected with the end of said link lever carrying said driving means, whereby the rotation of the lever arm expands the pantographic lifting mechanism.

2. Lifting apparatus according to claim 1, wherein the driving means comprises a hydraulic cylinder, sprocket wheels connected to the lever arm, and a chain or chains engaged with the sprocket wheels and connected to the piston rod of said hydraulic cylinder.

3. Lifting apparatus according to claim 1, further comprising a V-shaped actuating member connected to the end of said lever arm at the corner thereof, an auxiliary rod connected to an end of the actuating member and to the link lever, and a roller provided on the other end of said actuating member to be engaged with said link lever.

4. Lifting apparatus substantially as herein described with reference to the accompanying drawings.